The accumulation of nitrates is a major problem in both salt and fresh water aquariums and similar aquatic environments. Nitrates build up rapidly in these environments due to fish waste and the regular addition of food, which contains nitrogenous compounds. At high enough concentrations, nitrates are noxious to aquatic life. To address this problem, polluted water from aquariums is replaced with new water frequently in order to maintain a healthy aquarium. The dumping of nitrate polluted water into the environment furthers the nitrate pollution of water supplies worldwide. This water changing is time consuming and may be expensive to both aquatic hobbyists and keepers of commercial aquariums alike, especially if the aquarium is a salt water aquarium that is not in close proximity to the ocean or other sources of unpolluted aquarium water.
Various methods, other than water changes, are known in the art for removing nitrates from aquariums. One common method is the use of protein skimmers to eliminate nitrogenous compounds before they are transformed into nitrates. Protein skimmers are constructed in a tube or tower having a collection cup at the top. These skimmers work by injecting massive amounts of very fine air bubbles into the tube. The rising air bubbles act as a lift in the tube, allowing the undesirable nitrogenous compounds to attach to the bubbles and rise to the surface, where they are captured in the collection cup and disposed of.
Another method for reducing nitrates involves using bacteria. Examples of such systems are described in U.S. Pat. No. 4,995,980, to Jaubert; an article entitled “Nitrates Elimination by Autotrophic Denitration on Sulfur,” by Christophe Soler; and an article by Marck Langouet, entitled, “The Autotrophic Denitration on Sulfur What's the Status?.”